JPH0340922B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a permanent magnet. More specifically, it relates to a method for manufacturing polycrystalline manganese-aluminum-carbon (Mn-Al-C) alloy magnets, particularly Mn-Al-C for high-performance multipole magnetization.
The present invention provides a method for manufacturing alloy magnets.

Mn-Al-C alloy magnets are mainly composed of a face-centered tetragonal (τ phase, L _10- type regular lattice) structure, which is a ferromagnetic phase, and contain C as an essential constituent element. Multi-component alloy magnets are known, including ternary alloy magnets containing no additive elements and quaternary or higher alloy magnets containing a small amount of additive elements. Furthermore, as a manufacturing method for this Mn--Al--C alloy magnet, there is known a method that includes a warm plastic working process such as warm extrusion, in addition to the method of casting and heat treatment. In particular, the latter method is known as a method for producing anisotropic magnets having excellent properties such as high magnetic properties, mechanical strength, weather resistance, and machinability.

Methods for producing multipolar magnetized Mn-Al-C alloy magnets include isotropic magnets, compression processing, and uniaxially anisotropic polycrystals obtained in advance by known methods such as warm extrusion processing. It is known that Mn--Al--C alloy magnets are subjected to warm free compression processing in an anisotropic direction (combined processing method).

Compression processing provides high magnetic properties in the radial direction, but requires a relatively large processing rate and may cause non-uniform deformation.
There are problems such as the unavoidable existence of an indeformable zone. With the combined processing method, high magnetic properties are obtained in all directions within the plane, including the radial and chordal directions, with small compressive strain. The magnet obtained by the composite processing method has an easy magnetization direction parallel to a specific plane, is magnetically isotropic within the plane, and includes a line perpendicular to the plane and a straight line parallel to the plane. It has a structure that is anisotropic in a plane (hereinafter, such a magnet will be referred to as a plane anisotropic magnet).

The shape of a multipolar magnetized magnet is generally a cylindrical body, and the main magnetization methods include those shown in FIGS. 1 and 2. FIG. 1 schematically shows the shape of the magnetic path (represented by broken lines) inside the magnet when the outer periphery of the cylindrical magnet is magnetized with multiple poles. Similarly, FIG. 2 shows the case where the inner periphery is multipole magnetized. In this specification, the magnetization shown in FIG. 1 is referred to as outer circumference magnetization, and the magnetization shown in FIG. 2 is referred to as inner circumference magnetization.

As shown in FIG. 1, in the case of outer periphery magnetization, the magnetic path runs approximately along the radial direction at the outer periphery of the magnet, and approximately along the chord direction at the inner periphery. On the other hand, as shown in FIG. 2, the inner circumferential magnetization is the opposite of the above. On the other hand, as mentioned above, planar anisotropic magnets have high magnetic properties in all directions within the plane, including the radial and chordal directions. Considering the magnetic path at , the anisotropic structure is not necessarily suitable for individual magnetization.

The present inventors have developed a method that has an easy magnetization direction parallel to a specific plane, is magnetically isotropic within the plane, and has a straight line parallel to the direction perpendicular to the plane and the specific plane. Polycrystalline Mn-Al-C alloy magnet (planar anisotropic magnet) that is anisotropic in the plane containing
It has been found that the above-mentioned problems can be solved by subjecting a billet made of the above-mentioned material to plastic working at a temperature of 530 to 830 DEG C. in which compressive strain is applied to a portion of the billet in a direction parallel to the perpendicular line.

That is, a known Mn-Al-C alloy for magnets,
For example, with 68~73 wt% Mn (1/10Mn−6.6)~
(1/3Mn-22.2) An alloy consisting of C in the weight percent and the balance in Al was made into a uniaxial, homogeneous, fine [001] fiber structure by a known method such as extrusion at a temperature range of 530 to 830℃. After that, the above-mentioned plane anisotropic magnet can be obtained by further free compression processing in which a compressive strain of 0.1 or more is applied in the absolute value of the logarithmic strain in a direction parallel to the axial direction.

Billets made of planar anisotropic magnets are heated to 530 to 830℃.
By applying plastic working to a portion of the billet at a temperature of It is possible to obtain a magnet having magnetic properties superior to those of magnetic magnets.

To explain some specific examples of plastic working that applies compressive strain in a direction parallel to the perpendicular line to a part of a billet made of a planar anisotropic magnet, the first example is when the shape of the billet is cylindrical. An example of plastic working is shown in Fig. 3. FIG. 3 is a sectional view of the mold. Figure 3 shows the state during plastic working, with (a) showing before working and (b) showing after working. Third
In the figure, 1 is a billet, 2 is a movable punch, and 3 is a billet.
is a fixing punch, and 4 is a lower mold. By fixing and restraining the billet 1 with the fixing punch 2 and the lower die 4, and compressing only the outer periphery of the billet with the movable punch 2, the state shown in (b) is achieved.Second example Similarly to FIG. 3, FIG. 4 shows an example of plastic working when the shape of the billet is cylindrical. Figure 4 (a) shows the state before processing,
(b) shows the state after processing. In FIG. 4, 5 is a punch, 6 is an outer mold, and 7 is a lower mold. Billet 1
The billet is fixed and restrained by the outer mold 6 and the lower mold 7, and only the inner circumferential portion of the billet is compressed using the punch 5, so that the state shown in (b) is obtained.

In the first example described above, since compression was applied only to the outer circumference of the cylindrical billet, the outer circumference becomes a magnet that has higher magnetic properties in the radial direction than in the chordal direction, and the outer circumference magnetization shown in Figure 1 is This is a magnet that exhibits excellent properties when applied. In the second example, since compression was applied only to the inner circumference of the cylindrical billet, the inner circumference became a magnet with higher magnetic properties in the radial direction than in the chordal direction, and the inner circumference magnetization shown in Figure 2 was achieved. This is a magnet that exhibits excellent properties when applied. In the above example, the parts to be plastically worked are the outer circumferential part and the inner circumferential part according to Figs. 1 and 2, but when used for special purposes (magnetization other than Figs. By selecting an appropriate plastic working method, the anisotropic structure of the planar anisotropic magnet can be improved and made desirable.

The above-mentioned compression processing includes a method of performing compression processing continuously and a method of performing compression processing in multiple steps.

Regarding the temperature range in which plastic working is possible as mentioned above, plastic working was possible in the temperature range of 530 to 830°C, but at temperatures exceeding 780°C, the magnetic properties before plastic working and the processing Comparing the subsequent magnet properties, the plastic working significantly reduced the magnet properties. Furthermore, at temperatures below 530°C, the plastic workability was not good and the steel broke. Moreover, at temperatures below 560°C, many cracks occur during plastic working, and the desirable temperature range is 560 to 760°C.

Hereinafter, the present invention will be explained in detail with reference to Examples.

In the blended composition, 69.5% by weight of Mn, 29.3% by weight of Al,
A cylindrical billet with a diameter of 60 mm and a length of 50 mm was prepared by melting and casting 0.5% by weight of C and 0.7% by weight of Ni. After holding this billet at 1100℃ for 2 hours,
Heat treatment was performed by allowing the sample to cool to room temperature. Next, extrusion processing up to a diameter of 35 mm was performed at a temperature of 720° C. using a lubricant. Furthermore, extrusion processing up to a diameter of 24 mm was performed at a temperature of 680°C using a lubricant. After cutting this extruded rod to a length of 20 mm, it was subjected to free compression processing to a length of 10 mm at a temperature of 680°C via a lubricant. After processing, the billet was cut to a diameter of 32 mm and a length of 10 mm to produce a cylindrical magnet (planar anisotropic magnet).

This magnet was further molded using the mold shown in Figure 3.
Only the outer periphery was compressed at a temperature of 680℃. Third
In the figure, the inner diameter of the movable punch 2 (fixed punch 3
outer diameter) is 25 mm. The length of the outer periphery of the magnet after processing was 8 mm. The outer diameter of the magnet after processing is 32
It was cut into a cylindrical shape with an inner diameter of 10 mm and magnetized on the outer periphery with 24 poles. The magnetization was pulsed at 1500V using a 2000μF oil capacitor. The surface magnetic flux density at the outer periphery was measured using a Hall element. For comparison, a planar anisotropic magnet produced in the same manner as above was cut into a cylindrical shape with an outer diameter of 32 mm and an inner diameter of 10 mm, and magnetized in the same manner as above. Comparing the above two values, the value of the surface magnetic flux density of the magnet obtained by the method of the present invention was about 1.2 times that of the planar anisotropic magnet.

Next, we fabricated two planar anisotropic magnets using the same method as above, and cut them into pieces with an outer diameter of 32 mm, an inner diameter of 16 mm, and a length of
A 10mm cylindrical magnet was obtained. One of the cylindrical magnets was further compressed at a temperature of 680 DEG C. using the mold shown in FIG. 4. The length of the inner circumference after processing was 8 mm. In addition, in FIG. 4, the diameter of the punch 5 was 23 mm. The processed magnet was cut into a cylindrical shape with an outer diameter of 32 mm and an inner diameter of 16 cm. Furthermore, only the inner circumference was compressed. Two magnets, the magnet of the present invention and the planar anisotropic magnet, were magnetized with 18 internal poles. The magnetization conditions and measurement method are the same as described above. Comparing both values, the value of the surface magnetic flux density of the magnet obtained by the method of the present invention was about 1.2 times that of the plane anisotropic magnet.

As described in the embodiments, the present invention has an easy magnetization direction parallel to a specific plane, is magnetically isotropic within the plane, and has a direction perpendicular to the plane and the specific direction. A billet made of a polycrystalline Mn-Al-C alloy magnet (planar anisotropic magnet) which is anisotropic in a plane including a straight line parallel to the plane of By performing plastic working that applies compressive strain, it is possible to obtain a magnet that has magnetic properties superior to planar anisotropic magnets when subjected to various types of multipolar magnetization.

The permanent magnet obtained by the present invention is a magnet suitable for high-performance multipolar magnetization, and is suitable for motors, generators,
It can be applied to many fields such as meters.

[Brief explanation of drawings]

Figure 1 is a diagram schematically showing the formation of a magnetic path inside the magnet when the outer periphery of a cylindrical magnet is magnetized with multiple poles, and Figure 2 is a diagram showing the formation of a magnetic path inside the magnet when the outer periphery of the cylindrical magnet is magnetized with multiple poles. FIGS. 3 and 4 are cross-sectional views of a part of a mold showing an example of the plastic working of the present invention. 1... Billet, 2... Movable punch, 3... Fixed punch, 4... Lower mold, 5... Punch, 6...
Outer mold, 7...lower mold.

Claims (1)

[Claims] 1. It has an easy magnetization direction parallel to a specific plane, is magnetically isotropic within the plane, and is different in a plane containing a perpendicular line to the plane and a straight line parallel to the specific plane. A billet made of an orthotropic polycrystalline manganese-aluminum-carbon alloy magnet is subjected to plastic working at a temperature of 530 to 830°C to impart compressive strain to a portion of the billet in a direction parallel to the perpendicular line. A method for manufacturing a manganese-aluminum-carbon alloy magnet.